A railroad network normally contains one or more switchyards in which railcars are routed from tracks leading from a departure point to tracks going to a destination point. A typical switchyard has four main components, namely receiving tracks, a railcar switching mechanism, a set of classification tracks and a set of departure tracks. Incoming trains deliver railcars in the receiving tracks. The railcars are processed by the switching mechanism that routes individual railcars to respective classification tracks.
Two types of switching mechanisms are in use today. The first one is a hump switch. Switchyards that use a hump switch are referred to as hump yards. A hump switchyard uses a hump over which a railcar is pushed by a locomotive. At the top of the hump the railcar is allowed to roll on the other side of the hump under the effect of gravity. Retarders keep the railcar from reaching excessive speeds. The hump tracks on which the railcar rolls down the hump connect with the classification tracks. A track switch establishes a temporary connection between the hump tracks and a selected one of the classification tracks such that the railcar can roll in the classification tracks. A departure train is constituted when the requisite number of railcars has been placed in a set of classification tracks. When the departure train leaves the switchyard, the set of classification tracks become available for building a new departure train.
The second type of switch mechanism is a flat switch. The principle is generally the same as a hump yard except that instead of using gravity to direct railcars to selected classification tracks, a locomotive is used to push the railcar from the receiving tracks to the selected set of classification tracks.
In order to increase the efficiency of switching operations railway companies have developed the concept of railcar blocking. Under this concept, a block of railcars, hence the name “blocking”, may be logically switched as a unit in a switchyard. A block is established on a basis of certain properties shared by the railcars belonging to the block. For instance railcars that have a common destination point on their route can be blocked together. A “block” is therefore a logical entity that helps making switching decisions. For reference it should be noted that generally, two types of blocks exist. There is the so called “yard block” and a “train block”. For clarity, the term “block” alone in the present specification encompasses either a yard block or a train block.
The principle of blocking, either yard blocking or train blocking increases the efficiency with which railcars are processed at switchyards. However, it also brings constraints. Very often a train block must be assembled from railcars that arrive on different incoming trains. The train block will be complete and available for departure only when all the railcars that make up the train block have arrived at the switchyard. If one or more of the railcars are delayed the train block cannot be completed and the entire departure train that pulls this train block may leave without the delayed railcars. Such occurrence may create a cascading effect throughout entire segments of the railroad network and have significant financial repercussions for the railroad operator. Specifically, it is not uncommon for an operator to guarantee railcar arrival times to customers and delays incur financial penalties that may be significant.
In general switchyard operations planning is done either manually or via simple management tools. In order to increase the efficiency of those operations there is a need to provide an automated system that can forecast the outbound workload and thus provide the yard master with a projection of the traffic that can be available to departure trains.